In digital multi-function peripherals, there is a digital multi-function peripheral which has a function of storing data in a portable external memory connected by a user and carrying out image processing using the data of the external memory. Such a function is realized on condition that the user removes the external memory after the use. However, there exists a case where the user forgets to remove the external memory from the digital multi-function peripheral and leaves the external memory attached to the digital multi-function peripheral as it is, which may lead to a problem that the external memory is taken away by a third person, or that the data in the external memory is viewed by a third person.